1. Field of the Invention
This disclosure is related to the field of systems for the management of traffic flow through the controlling of signal lights and detection of travelers within a traffic grid. Specifically, the system relates to small vehicle and pedestrian interactions with controlled signal lights.
2. Description of the Related Art
In the perfect urban commuter's utopia, signal lights would automatically switch to green every time a driver or pedestrian approached an intersection, creating an unobstructed pathway towards the individual's final destination regardless of the type of vehicle—or lack of vehicle. However, in real life, encountering a red light, or “don't-walk” signal, is a normal and inevitable part of urban travel. With the growth of modern cities and the increasing number of bicycle lanes and pedestrian signals, efficient control of the ebb and flow of all traffic through efficient and smart signal-light control and coordination systems has become increasingly important.
There are many substantial benefits to be reaped from improved traffic flow for all types of vehicles. For many commuters, reclaiming part of their day would enhance their quality of life. Further, less congestion on the roads would generate fewer accidents, thereby saving lives. Moreover, traffic delays impinge on productivity and economic efficiency-time spent traveling to and from work is not time spent doing work. Further, many goods must be transported and many service providers must travel to their clients. Traffic delays all of these economic production factors.
There is also a concern regarding the increased pollution that results from motor vehicles in stop-and-go traffic compared to smooth flowing traffic. Further, longer commutes mean longer running times and also entail more greenhouse gas release. Further, congested traffic and uncoordinated signal lights can cause delays in a mass transit system which, if not remedied, can throw off an entire mass transit schedule grid and disincentive individuals from using mass transit systems. Lastly, the importance of prioritizing and efficiently moving emergency vehicles through traffic lights is axiomatic.
Currently, a variety of different control and coordination systems are utilized to ensure the smooth and safe management of traffic flows. One commonly utilized mechanism is the traffic controller system. In this system, the timing of a particular signal light is controlled by a traffic controller located inside a cabinet which is at a close proximity to the signal light. Generally, the traffic controller cabinet contains a power panel (to distribute electrical power in the cabinet); a detector interface panel (to connect to loop detectors and other detectors); detector amplifiers; a controller; a conflict motor unit; flash transfer relays; and a police panel (to allow the police to disable and control the signal), amongst other components.
Traffic controller cabinets generally operate on the concept of phases or directions of movement grouped together. For example, a simple four-way intersection will have two phases: North/South and East/West; a four-way intersection with independent control for each direction and each left hand turn will have eight phases. Controllers also generally operate on the concept of rings or different arrays of independent timing sequences. For example, in a dual ring controller, opposing left-turn arrows may turn red independently, depending on the amount of traffic. Thus, a typical controller is an eight-phase, dual ring controller.
The currently utilized control and coordination systems for the typical signal light range from simple clocked timing mechanisms to sophisticated computerized control and coordination systems that self-adjust to minimize the delay to individuals utilizing the roadways.
The simplest control system currently utilized is a timer system. In this system, each phase lasts for a specific duration until the next phase change occurs. Generally, this specific timed pattern will repeat itself regardless of the current traffic flows or the location of a priority vehicle within the traffic grid. While this type of control mechanism can be effective in one-way grids where it is often possible to coordinate signal lights to a desired travel speed, this control mechanism is not advantageous when the signal timing of the intersection would benefit from being adapted to the changing flows of traffic throughout the day and is generally no longer used in new traffic signal installations.
Dynamic signals, also known as actuated signals, are programmed to adjust their timing and phasing to meet the changing ebb and flow in traffic patterns throughout the day. Generally, dynamic traffic control systems use input from vehicle detectors to adjust signal timing and phasing. Detectors are devices that use sensors to inform the controller processor whether vehicles or other road users are present and waiting at the intersection. The signal control mechanism at a given light can utilize the input it receives from the detectors to adequately adjust the length and timing of the phases in accordance with the current traffic volumes and flows. The currently utilized detectors can generally be placed into three main classes: in-pavement detectors, non-intrusive detectors, and demand buttons for pedestrians.
In-pavement detectors are detectors that are located in or underneath the roadway. These detectors typically function similarly to metal detectors or weight detectors, utilizing the metal content or the weight of a vehicle as a trigger to detect the presence of traffic waiting at the light and, thus, can reduce the time period that a green signal is given to an empty road and increase the time period that a green signal is given to a busy throughway during rush hour. Non-intrusive detectors include video image processors, sensors that use electromagnetic waves or acoustic sensors that detect the presence of vehicles at the intersection waiting for the right of way from a location generally over the roadway and perform essentially the same function. Some models of these non-intrusive detectors have the benefit of being able to sense the presence of vehicles or traffic in a general area or virtual detection zone preceding the intersection as opposed to just those waiting. Vehicle detection in these zones can have an impact on the timing of the phases as they can often detect vehicles before they interact with the intersection.
The problems with the above systems, however, is that they are geared to detect motorized vehicles in standard motor vehicle lanes. In-ground detectors generally rely on a vehicle in a lane having enough metal to trigger a magnetic sensor and video systems generally rely on sufficient volume of an object to be detected as a motor vehicle. To deal with pedestrians, they are commonly supplied a demand button on the sidewalk to request an intersection light change and a crosswalk signal. However, bicyclists, particularly high performance bicycles, and other light vehicles such as mopeds or motorcycles, as well as highly modern car body designs, may not include enough metal to trigger in road systems and are commonly not allowed to travel on the sidewalk. Further, demand buttons still require the pedestrian to be waiting at, not approaching the intersection.
Bicyclists, in particular, can have problems with intersection detection systems because they are often in a specialized bike lane that actually lacks an in-ground detector, coverage from a video detector and, because they are not on a sidewalk like a pedestrian, do not have ready access to the demand buttons available for pedestrians. It is, thus, very possible for a bicyclist to be forced to sit at an intersection until a car comes along going the direction they wish to go, so that the detection system controlling the intersection can be activated. This regularly forces a bicyclist to either stay with a flow of motor vehicles that can trigger the intersection detection systems for it, or to hope that a motor vehicle is available at the intersection at the right time. This can make bicycle riding on less congested streets (which is often preferred from a safety point of view) a frustrating experience because the bicyclist is constantly being forced to stop at intersections (making the ride more difficult) and waiting when there is no need.
This lack of control of intersection lights not only creates frustration, but can create dangerous situations. Bicyclists aware that they can't change an intersection to match their needs, may attempt to simply run it on yellow or red or to go faster than they should to keep up with a motor vehicle that will change the light. Alternatively, bicyclists may ride on a sidewalk so they can trigger demand buttons or may choose to ride on more congested roads where motor vehicle traffic is more likely to trigger intersections for them in a beneficial way.
Above and beyond detectors for individual signal lights, coordinated systems that string together and control the timing of multiple signal lights are advantageous in the control of traffic flow within more urban areas. Generally, coordinated systems are controlled from a master controller and are set up so that lights cascade in sequence, thereby allowing a group or “platoon” of vehicles to proceed through a continuous series of green lights. Accordingly, these coordinated systems make it possible for drivers to travel long distances without encountering a red light dramatically improving traffic flow. They also encourage adherence to posted speed limits as such adherence results in less stoppage. Generally, on one-way streets this coordination can be accomplished with fairly constant levels of traffic. Two-way streets are more complicated, but often end up being arranged to correspond with rush hours to allow longer green light times for the heavier volume direction or to have longer greens on larger roads with shorter sections on cross streets.
The most technologically advanced coordinated systems control a series of city-wide signal lights through a centrally controlled system that allows for the signal lights to be coordinated in real-time through sensors that can sense the levels of traffic approaching and leaving a virtual detection zone which precedes a particular intersection. Often these types of systems get away from algorithmic control of traffic patterns (e.g. where platoons are created based on expected traffic flow regardless of whether vehicles are actually present) to priority systems where the priority of any particular motor vehicle at any intersection at any instant can be determined to improve flow. Priority systems allow for very high priority vehicles, such as emergency vehicles, to have unimpeded access even in heavy traffic conditions, and in the best of these systems, traffic flow through the entire grid is changing all the time based on the location of vehicles in the system and determinations of how best to maximize the movement of the most number of vehicles.
While cascading or synchronized central control systems with priority are an improvement on the traditional timer controlled systems, they still have their drawbacks. Namely, very high priority vehicles (e.g. emergency vehicles) in these systems are often only able to interact with a detection zone immediately preceding a particular intersection; there is no real-time monitoring of the traffic flows preceding or following this detection zone across a grid of multiple signal lights. Stated differently, there is no real-time monitoring of how a single vehicle or a group of vehicles travels through a traffic grid as a whole (i.e., approaching, traveling through and leaving intersections along with a vehicle's transit between intersections). Accordingly, these systems can provide for a priority vehicle, such as an emergency vehicle, to be accelerated through a particular signal at the expense of other vehicles, but they can lack the capability to adapt and adjust traffic flows to respond to the fact that the emergency vehicle has disrupted the flow by its passage.
If a priority vehicle is sensed in the detection zone, the immediately upcoming light will generally change to green to give the priority vehicle the right-of-way and potentially disrupt the entire system. While this is generally logical for allowing rapid passage of an emergency vehicle where disruption is an acceptable inconvenience for insuring timely emergency services, another issue of disruption not taken into account is pedestrian, bicycle, and other light vehicle traffic. Pedestrian demand buttons need to have an effect on traffic flow to allow for pedestrian movement, but if they actual provide for demand services, are effectively the equivalent of a high priority vehicle and can disrupt a coordinated traffic flow.
There are many substantial benefits to be reaped from improved non-motorized traffic flow for individual commuters in urban areas. These benefits are clearest as a part of a traffic grid with coordinated signals, that is, successive intersections that adjust signal timing to grant more green-light time for directions with heavy traffic. A traffic grid with coordinated signals, granting the same consideration to motorized as well as smaller vehicles, bicycles, or pedestrians, offers commuters multiple options for their selected mode of travel, reducing motorized traffic and resulting in less congestion. Congested traffic, and uncoordinated, or unreliable coordination of signals increase travel times and disincentive individuals from smaller, more energy-efficient modes of travel. These other travel modes contribute lower amounts of greenhouse gas pollution. Additionally, travelers that encounter fewer red lights, also have fewer opportunities to cross intersections against the red signal, reducing the likelihood of accidents.
Accordingly, there is a need in the art for a safety system which can be utilized by both travelers and traffic agencies, that has the ability to detect when a traveler, as opposed to a vehicle, is approaching, or at, an intersection and to communicate their presence to the signal equipment responsible for controlling that intersection so that they can all have similar interactions with a priority system. The signal controller may be programmed to alter the timing phases for the intersection to grant passage to those individuals according to the traffic standards for the given area to provide priority to different types of vehicles at different times.